I have a R920 server. It used to be running with two E7-8891v2 CPUs and sixteen 2Rx8GB RAM sticks totaling 128GB across 4 risers. I recently added two additional E7-8891v2 CPUs and filling the remaining riser slots. I spread the RAM sticks evenly across the 8 risers, filling slots 1s and 2s, providing 32GB to each CPU.

When I boot with this new configuration, I get the following error message:

Socket[2] Warning! Major Code: 0x33 Minor Code: 0x01, LogData: 0x0401FFFF
Riser F SMI2 initialization failure.
DC detect failure.
Riser F even number DIMMs disabled.
Please remove and reseat memory riser.

I have tried the following:

1. Rearranging the risers.
2. Rearranging the memory modules in the risers.
3. Swapping the two new CPUs.

It consistently complained about riser F.

Does anyone have a suggestion on how to further troubleshoot this?